In recent years, in a 3rd generation partnership project (3GPP), a standard technology for utilizing a long term evolution (LTE) system that operates in a conventional licensed band used in an unlicensed band of 5 GHz has been developed. A scenario that aggregates and operates carriers of the licensed band and the unlicensed band is first reviewed and Duplex of the unlicensed band considers a time division duplex (TDD) mode considering a downlink or both an uplink and a downlink of frequency-division duplex (FDD).
3GPP LTE is a system in which a base station (eNodeB) controls all resources and the downlink thereof distributes/allocates different resources to a terminal (UE) through orthogonal frequency division multiple access (OFDMA) and the uplink thereof distributes/allocates different resources to the terminal (UE) through single carrier frequency division multiple access (SC-FDMA).